When mobility in a network is performed during communication using an IP, a Mobile IP is available as technology for continuing the communication without having to change an IP address (refer to Non-Patent Literature 1).
Non-Patent Literature 1
“IP Mobility Support for IPv4,” RFC3344, August, 2002.
An MN (Mobile Node) notifies an HA (Home Agent) which is present in the home network of the MN of an address acquired during a network connection as a CoA (Care-of-Address). The HA is allowed to communicate by receiving and transferring a packet destined for the MN by proxy, while the MN is allowed to communicate by using an HoA (Home Address) used when the MN is present in the home network.
Furthermore, where the MN functions as a router of a local network, the MN operates as follows.
When a communication terminal MNN (Mobile Network Node) is connected to a network under the control of the MN, the MNN acquires an address managed by the MN through DHSP, PPP, and the like. The MN notifies the HA of an address assigned thereby, while the HA registers so as to transfer a packet destined for the assigned address as well.